Technology for predicting body measurements of a person, with a full body photo of them
If the user will be imputting the body height/largest width measures, and you want to have a couple of groups where you final results will be stored at, you should look at the classification algorithms(Logistic Regression, KNN, Random Forests).
If on the other hand, you want your program to detect the user from an image and take the measurements itself, you would need to look into Convolutional Neural Networks, along with person detection/segmentation